Diesel engine overheat

[jrb551]

Is anyone familiar with Deutz 2011 family of oil-cooled diesel engines? I am having trouble trying to figure out why I am seeing the 4cyl turbo model continually overheat. Usually it is in the number one cyl (flywheel end). Symptoms are burnt, melted piston top and 4 point scoring in the number 1 and sometimes other cyl walls. Radiator cooling capacity seems to be there but the engine is in an application where it sees a heavy duty cycle. Any ideas?

 

[MikeHalloran]

One distributor's page characterizes the 2011 as 'new' and 'innovative'.

I take that to mean that they laid off all the guys who actually knew how to design engines, and this is the first effort of the replacement neophytes.

Seriously, I'd suggest getting the application engineering data for the engine(s) you have, and checking it against the application they're in.



Mike Halloran
Pembroke Pines, FL, USA

 

[jrb551]

Thanks Mike. I've done that and everything seems to check out ok. In fact, we have exceeded the heat rejection requirements by a very large margin so we should be running cool as a cucumber. It seems like we must be seeing problems with either:
1.) fuel delivery (over or under fueling)
2.) thermostat not opening quick enough
3.) insufficient oil flow through cyl heads to provide adequate cooling
We also know we have a problem with the temperature/shutdown switch. It is a 135C switch but it frequently allows the oil temp to get all the way up to 150C before switching. The thing is, I can't understand how the engine ever builds enough heat to cook itself given the radiator sizing.
Do you think it's possible that under a heavy duty cycle, the engine burns so much fuel that the motor oil it uses to cool itself can't carry away enough heat?

 

[MikeHalloran]

Given the nature of the coolant, I'd guess that a head gasket leak could result in overfueling.

Did the engine overheat since new, or just since a top end overhaul?

Have you spoken with a Deutz rep about the problem?



Mike Halloran
Pembroke Pines, FL, USA

 

[ccfowler]

jrb551,

One of the first things that I would want to verify is the actual oil being used. Is it actually the proper oil? The actual oil used may be too viscous either by deliberate choice or by poor oil quality control.

A problem that I have encountered several times is the substitution of more viscous lube oil in "hot" applications. The innocent concern was that the oil would not have adequate viscosity to protect lubricated surfaces, so thicker oil was deliberately used. In reality, the more viscous oil produced inferior lubrication and even higher temperatures due to diminished flow and diminished oil cooler performance. Another problem with more viscous lube oil is poor spray patterns, poor splash distribution, and dimished flows for cooling.

I can readily imagine a situation such as yours where "low oil pressure" was noticed, and heavier oil was substituted to "correct" that "problem." If so, it is likely that the indicated oil pressure was then restored by effectively restricting the flow where it was needed while a significant portion of the oil pump's delivery was by-passed through the pressure relief valve.